I am relatively new to Cocoa programming. Basically, I want to send a message within a method in my Document class to an intense of a class (that inherits from NSView) that I have initialised as a property in the #interface of the Document class.
Here is the simplified version:
///////////////////////////KOZDocument.h///////////////////////////
#import <Cocoa/Cocoa.h>
#import "KOZOtherClass.h"
#interface KOZDocument : NSDocument
#property (assign) IBOutlet KOZOtherClass *otherClassInstance; //this would be connected to the relevant CustomView in the IB
#end
///////////////////////////KOZDocument.m///////////////////////////
#import "KOZDocument.h"
#implementation KOZDocument
- (id)init
{
self = [super init];
if (self) {
// I want to send a message to otherClassInstance from some method e.g. init
NSLog(#"INITIALISING");
[[self otherClassInstance] printMessage];// this is the message I want to work but which doesn't (even though i don't any errors)
//sending the message to a locally initiated instance works but I don't want to use a local instance because i want to connect it to a CustomView in IB
KOZOtherClass *otherClassLocalInstance = [[KOZOtherClass alloc] init];
[otherClassLocalInstance printMessage];
}
return self;
}
//.….
///////////////////////////KOZOtherClass.h///////////////////////////
#import <Foundation/Foundation.h>
#interface KOZOtherClass : NSView
- (void) printMessage;
#end
///////////////////////////KOZOtherClass.m///////////////////////////
#import "KOZOtherClass.h"
#implementation KOZOtherClass
- (void) printMessage{
NSLog(#"This method can be called!!");
}
#end
/////////////////////////////////////////////////////////////////////
The same methodology works for all the native Cocoa objects but not for mine.
Can anyone tell me what I'm doing wrong?
Here is the context of why i want to do this:
I am building an app that plays a video using the AVFoundation. I have an animation I want to trigger in an NSView when the playback reaches a particular part in the video (e.g. after 2 seconds). I am adapting Apple's AVSimplePlayer and using the time observer to get the position of the playhead. The time observer executes the code inside a block for every given time interval. In this block I want to send a message to my animation view to trigger the animation when the time is more that 5 seconds for example.
In -init of your objects the Interface Builder connections are not set yet, the loading mechanism can't set those before your object is initialized.
Instead you want to overwrite the -awakeFromNib method like so:
- (void)awakeFromNib {
[[self otherClassInstance] printMessage];
}
-awakeFromNib is guaranteed to be called after the connections have been made. Depending on the exact implementation you may also need to guard against that code being executed twice, for example by having a boolean instance variable didWake that you check/set in that method.
Related
I have a main window with a couple of popupbuttons. I want to clear them, then load the lists from a method in a custom class. I've got my view controller working and I know the method in the custom class (newRequest) is working because I added a NSLog command to print "Test" when the method executes. In AppDelegate I'm calling the method via:
[polyAppRequest newRequest];.
As I said, I know the method is executing. Why can't I removeallitems from the popupbutton from this custom class method?
Thanks
Keith
I read that you should use an NSWindowController to manage a window. See here:
Windows and window controllers
Adding views or windows to MainWindow
Then if your window gets complicated enough, the NSWindowController can employ various NSViewControllers to manage parts of the window.
In any case, I used an NSWindowController in my answer.
The image below shows the outlet's for File's Owner, which is my MainWindowController:
I created MainWindowController .h/.m in Xcode6.2 by:
Selecting File>New>File>OS X - Source - Cocoa Class
Selecting NSWindowController for Subclass of:
Checking also create .xib file for user interface
Then I deleted the window--not the menu--in the default MainMenu.xib, and I changed the name of MainWindowController.xib, created by the steps above, to MainWindow.xib.
The following code works for me (but I'm a Cocoa beginner!):
//
// AppDelegate.m
// PopUpButtons
#import "AppDelegate.h"
#import "MainWindowController.h"
#interface AppDelegate ()
#property(strong) MainWindowController* mainWindowCtrl;
#end
#implementation AppDelegate
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
// Insert code here to initialize your application
[self setMainWindowCtrl:[[MainWindowController alloc] init]];
[[self mainWindowCtrl] showWindow:nil];
}
- (void)applicationWillTerminate:(NSNotification *)aNotification {
// Insert code here to tear down your application
}
#end
...
//
// MainWindowController.m
// PopUpButtons
//
#import "MainWindowController.h"
#import "MyData.h"
#interface MainWindowController ()
#property(strong) MyData* data;
#property(weak) IBOutlet NSPopUpButton* namePopUp;
#property(weak) IBOutlet NSPopUpButton* agePopUp;
#end
#implementation MainWindowController
-(id)init {
if (self = [super initWithWindowNibName:#"MainWindow"]) {
_data = [[MyData alloc] init]; //Get data for popups
}
return self;
}
- (void)windowDidLoad {
[super windowDidLoad];
// Implement this method to handle any initialization after your window controller's window has been loaded from its nib file.
[[self namePopUp] removeAllItems];
[[self namePopUp] addItemsWithTitles:[[self data] drinks]];
[[self agePopUp] removeAllItems];
[[self agePopUp] addItemsWithTitles:[[self data] extras]];
}
#end
...
//
// MyData.h
// PopUpButtons
//
#import <Foundation/Foundation.h>
#interface MyData : NSObject
#property NSArray* drinks;
#property NSArray* extras;
#end
...
//
// MyData.m
// PopUpButtons
//
#import "MyData.h"
#implementation MyData
- (id)init {
if (self = [super init]) {
_drinks = #[#"coffee", #"tea"];
_extras = #[#"milk", #"sugar", #"honey"];
}
return self;
}
#end
I hope that helps. If you need any more screenshots, let me know.
Edit1:
I think I see what you are asking about. Although I don't think it is a very good approach, if I change my code to this:
//
// MyData.h
// PopUpButtons
//
#import <Cocoa/Cocoa.h>
#interface MyData : NSObject
#property (copy) NSArray* drinks;
#property (copy) NSArray* extras;
-(void)newRequest;
#end
...
//
// MyData.m
// PopUpButtons
//
#import "MyData.h"
#interface MyData()
#property (weak) IBOutlet NSPopUpButton* drinksPopUp;
#property (weak) IBOutlet NSPopUpButton* extrasPopUp;
#end
#implementation MyData
- (id)init {
if (self = [super init]) {
_drinks = #[#"coffee", #"tea"];
_extras = #[#"milk", #"sugar", #"honey"];
}
return self;
}
-(void)newRequest {
[[self drinksPopUp] removeAllItems];
[[self drinksPopUp] addItemsWithTitles:[self drinks]];
[[self extrasPopUp] removeAllItems];
[[self extrasPopUp] addItemsWithTitles:[self extras]];
}
#end
I am unable to populate the NSPopUpButtons. This is what I did:
I dragged an Object from the Object Library to the dock in IB, and in the Identity Inspector, I changed the Object's class to MyData.
Then I clicked on the Connections Inspector, and the two instance variables in MyData, drinksPopUp and extrasPopUp, were listed in the Outlets.
I dragged from the outlets to the respective NSPopUpButtons.
I guess I assumed, like you, that when my program ran, the NSPopUpButtons would be assigned to the instance variables drinksPopUp and extrasPopUp--but that doesn't seem to be the case. According to the Apple docs, you should be able to do that:
An application typically sets outlet connections between its custom
controller objects and objects on the user interface, but they can be
made between any objects that can be represented as instances in
Interface Builder,...
Edit2:
I am able to pass the NSPopUpButtons from my MainWindowController to the newRequest method, and I can use the NSPopUpButtons inside newRequest to successfully populate the data.
Edit3:
I know the method in the custom class (newRequest) is working because
I added a NSLog command to print "Test" when the method executes.
But what happens when you log the variables that point to the NSPopUpButtons? With my code in Edit1, I get NULL for the variables, which means the NSPopUpButtons never got assigned to the variables.
Edit4:
If I add an awakeFromNib method to MyData, and inside awakeFromNib I log the NSPopUpButton variables for the code in Edit1, I get non NULL values. That tells me that the MainWindowController's windowDidLoad method is executing before MyData's awakeFromNib method, and therefore you cannot call newRequest inside MainWindowController's windowDidLoad method because MyData has not been fully initialized.
Edit5:
Okay, I got the code in Edit1 to work. The Apple docs say this:
About the Top-Level Objects
When your program loads a nib file, Cocoa recreates the entire graph
of objects you created in Xcode. This object graph includes all of the
windows, views, controls, cells, menus, and custom objects found in
the nib file. The top-level objects are the subset of these objects
that do not have a parent object [in IB]. The top-level objects typically
include only the windows, menubars, and custom controller objects that
you add to the nib file [like the MyData Object]. (Objects such as File’s Owner, First
Responder, and Application are placeholder objects and not considered
top-level objects.)
Typically, you use outlets in the File’s Owner object to store
references to the top-level objects of a nib file. If you do not use
outlets, however, you can retrieve the top-level objects from the
nib-loading routines directly. You should always keep a pointer to
these objects somewhere because your application is responsible for
releasing them when it is done using them. For more information about
the nib object behavior at load time, see Managing the Lifetimes of
Objects from Nib Files.
In accordance with the bolded line above, I changed this declaration in MainWindowController.m:
#interface MainWindowController ()
#property(strong) MyData* data;
...
#end
to this:
#interface MainWindowController ()
#property(strong) IBOutlet MyData* data;
...
#end
Then, in IB I dragged a connection from the MainWindowController data outlet to the MyData Object(the Object I had previously dragged out of the Object Library and onto the doc).
I guess that causes MyData to unarchive from the .xib file and initialize before MainWindowController.
This is a common topic but, in my case there is one thing I don't understand that I can't find explained in the other asked questions.
Here is the gist of what I'm trying to do:
User clicks a button and something like this is called:
#implementation FirstClass
-(void)clickedButton
{
[SecondClass changeText];
}
And then in SecondClass is:
#implementation SecondClass
- (void)changeText {
[myLabel setText:#"text"];
}
So when the user clicks the button, the text property in myLabel in SecondClass changes to "text".
The only problem I have with this is calling [SecondClass changeText] on the existing instance of SecondClass. Since I'm not initializing the CCNodes programmatically (they are all automatically loaded upon running the app), I don't know where or how SecondClass is initialized. I'm using SpriteBuilder to build this project.
Any help would be appreciated. Thanks!
So, you have two instaces -- one with a button, and one with a label. I'm assuming they are both descendants of NSViewController or otherwise manage underlying views.
The problem is, you found no way to address second instance containing label from the method of first instance.
You need to define a property in first instance's class:
#property(weak) SecondClass *secondInstance;
And then in button clicked method:
-(void)clickedButton
{
[self.secondInstance changeText];
}
There is one issue left: who is responsible to set first instance's property that we defined? This depends on who did create both of them, probably just app delegate or enclosing controller, you know that better.
UPD: If both of the controllers are created by AppDelegate:
#import "FirstClass.h"
#import "SecondClass.h"
#interface AppDelegate ()
// case A - manual
#property(strong) FirstClass *firstInstance;
#property(strong) SecondClass *secondInstance;
// case B - declared in xib
//#property(weak) IBOutlet FirstClass *firstInstance;
//#property(weak) IBOutlet SecondClass *secondInstance;
#end
#implementation AppDelegate
...
- (void)applicationDidFinishLaunching:(NSNotification *)notification
{
// Create them
self.firstInstance = [[FirstClass alloc] init...];
self.secondInstance = [[SecondClass alloc] init...];
// Or maybe they are declared in MainMenu.xib, then you do not create them
// by hand, but must have outlets for both. See case B above.
// Connect them
self.firstInstance.secondInstance = self.secondInstance;
...
}
Note that class is not the same as an object (instance). Class is a named collection of methods, mostly for the instance. In Objective-C, class is not just a name, but an object too, so you can call a method on it (i.e. send an message to the class object). But here we always talk about objects (instances), so forget about classes – we hold objects via strong properties or weak outlets, depending on how they were created, and operate on objects, never on classes.
In objective C, the methods are either instance methods or class methods. As the name suggests, the instance methods require an instance of the class to work, whereas the class methods can be used with just the name of the class. What you need here is a class method. Just change the following line in your code:
#implementation SecondClass
- (id)changeText {
to
#implementation SecondClass
+ (id)changeText {
This will change the method from an instance method to a class method.
SORRY FOR THE LENGTH OF THIS POST; IT IS MEANT TO DOCUMENT MY JOURNEY WITH THIS PROBLEM.
I have a question about a shared object in a Cocoa app that needs to change from time to time and how best to store it so that it's accessible from a few different places. Bear with me.
Class Implementation
The shared object is implemented as a Class Cluster (i.e., https://stackoverflow.com/a/2459385/327179) that looks like the following (note that Document is merely a class name; it is not necessarily indicative of what my actual class does):
In Document.h:
typedef enum {
DocumentTypeA,
DocumentTypeB
} DocumentType;
#interface Document : NSObject {}
- (Document *) initWithDocumentType:(NSUInteger)documentType;
- (void) methodA;
- (void) methodB;
#end
In Document.m:
#interface DocumentA : Document
- (void) methodA;
- (void) methodB;
#end
#interface DocumentB : Document
- (void) methodA;
- (void) methodB;
#end
#implementation Document
- (Document *)initWithDocumentType:(NSUInteger)documentType;
{
id instance = nil;
switch (documentType) {
case DocumentTypeA:
instance = [[DocumentA alloc] init];
break;
case DocumentTypeB:
instance = [[DocumentB alloc] init];
break;
default:
break;
}
return instance;
}
- (void) methodA
{
return nil;
}
- (void) methodB
{
return nil;
}
#end
#implementation DocumentA
- (void) methodA
{
// ...
}
- (void) methodB
{
// ...
}
#end
#implementation DocumentB
- (void) methodA
{
// ...
}
- (void) methodB
{
// ...
}
#end
How The User Interacts with a Document
Via a menu item, the user can switch between DocumentA and DocumentB at will.
What Happens When A "Switch" Occurs
When the user switches from, say, DocumentA to DocumentB, I need two things to happen:
My primary NSViewController (MainViewController) needs to be able to use the new object.
My AppDelegate needs to update an NSTextField that happens to be located in the content border of the main window. (FWIW, I can only seem to assign an outlet for the NSTextField in the AppDelegate)
The Question(s)
I've seen singletons mentioned quite a bit as a way to have a global reference without cluttering up one's AppDelegate (primarily here and here). That said, I've not seen much info on overwriting such a singleton (in our case, when a user switches from DocumentA to DocumentB [or vice versa], this global reference would need to hold the new object). I'm not an expert on design patterns, but I do remember hearing that singletons are not meant to be destroyed and recreated...
So, given all this, here are my questions:
How would you store my Class Cluster (such that MainViewController and AppDelegate can access it appropriately)?
Am I mixing concerns by having both MainViewController (who uses Document heavily) and AppDelegate (who manages the primary window [and thus, my NSTextField]) have knowledge of Document?
Feel free to let me know if I'm thinking about this problem incorrectly; I want this implementation to be as orthogonal and correct as possible.
Thanks!
Status Update #1
Thanks to advice from #JackyBoy, here's the route I've taken:
Document is the one that, upon "switching", "notifies" AppDelegate and MainViewController by passing them the newly created instance.
Both AppDelegate and MainViewController can update the Document object via the Singleton instance as necessary.
Here are my new files (dumbed down so that y'all can see the crux of the matter):
In Document.h:
#import <Foundation/Foundation.h>
#class AppDelegate;
#class MainViewController;
typedef enum {
DocumentTypeA,
DocumentTypeB
} DocumentType;
#interface Document : NSObject
#property (weak, nonatomic) MainViewController *mainViewControllerRef;
#property (weak, nonatomic) AppDelegate *appDelegateRef;
+ (Document *)sharedInstance;
- (id)initWithParser:(NSUInteger)parserType;
#end
In Document.m:
#import "AppDelegate.h"
#import "Document.h"
#import "MainViewController.h"
#interface DocumentA : Document
// ...
#end
#interface DocumentB : Document
// ...
#end
#implementation Document
#synthesize appDelegateRef;
#synthesize mainViewControllerRef;
+ (Document *)sharedInstance
{
static XParser *globalInstance;
static dispatch_once_t predicate;
dispatch_once(&predicate, ^{
// By default, I return a DocumentA object (for no particular reason).
globalInstance = [[self alloc] initWithDocumentType:DocumentA];
});
return globalInstance;
}
- (id)initWithDocumentType:(NSUInteger)documentType
{
Document *instance = nil;
switch (parserType) {
case DocumentTypeA:
instance = [[DocumentA alloc] init];
break;
case DocumentTypeB:
instance = [[DocumentB alloc] init];
break;
default:
break;
}
// QUESTION: Is this right? Do I have to store these references
// every time a new document type is initialized?
self.appDelegateRef = (AppDelegate *)[NSApp delegate];
self.mainViewControllerRef = self.appDelegateRef.mainViewController;
[self.appDelegateRef parserSwitchedWithParser:instance];
[self.mainViewControllerRef parserSwitchedWithParser:instance];
return instance;
}
#end
#implementation Xparser_NSXML
// ...
#end
#implementation DocumentA
// ...
#end
Should I be bothered by the fact that Document has knowledge of the existence of AppDelegate and MainViewController? Additionally, should I be bothered by the fact that when the Document object updates, it re-notifies both AppDelegate and MainViewController (even though one of those initiated the update)?
As always, I appreciate everyone's eyeballs on this as my quest for the ideal implementation continues. :)
Status Update #2
A comment from #Caleb helped me understand that an NSNotification-based setup would be a lot less unwieldy for this particular problem.
Thanks, all!
I don't see he need for a shared object here, much less a singleton. Do you really need to find the current Document at arbitrary times from many different objects? Seems more like you just have two objects (app delegate and view controller) that both need to know about the current Document. Notifications provide an easy way to manage that: whenever a switch happens, you can post a NSNotification that includes the new Document. Any objects that need to know about the current Document will have registered for the "document switch" notification, and when the notification arrives they can stash a pointer to the Document in an instance variable or property.
I do remember hearing that singletons are not meant to be destroyed
and recreated...
Well, you can have references inside of it, so you are not actually "destroying" the singleton, but the objects he points to. I tend to leave the App Delegate without application logic, so I normally put it somewhere else. In your case, since you need to access something from different places, it makes sense to have one. About the cluster, you can still have it, you just ask the singleton to access it and return the appropriate object like so:
Document *myDocument = [[MySingleton defaultManager] createObjectWithType:aType];
You gain some things out of this:
you can access your cluster from any place in your app
you decouple things, only one entity knows about your cluster.
Inside the Singleton you can have a reference to you AppDelegate and interact with it.
Inside the Singleton you can have a reference to the objects that are being used (Document A, Document B)
One more thing, I would advise putting the cluster access method as a class method (instead of an instance one).
So, I have a decent idea of what a delegate does, why use it, how to implement it etc. and I'm working on implementing it in one of my projects. The problem I'm trying to solve is to decouple my Controller objects from my Network Access class. In this context, the ideas get a little messy in my head.
I somehow intuitively feel that the NetworkAccessClass should be the delegate for a Controller object, because the NetworkAccessClass is acting as a helper for the Controller object. But it seems to work in a reverse fashion, because the following is apparently the right way to do it:
NetworkaccessClass.h
#protocol NetworkAccessDelegate
-(void) requestSucceded:(NSData *) data
-(void) requestFailed:(int) responseCode;
#end
#interface NetworkAccessClass : NSObject
{
id<NetworkAccessDelegate> networkDelegate;
}
#property(nonatomic, assign) id networkDelegate;
-(void) initWithDelegate:(id) delegate; //
#end
NetworkAccessClass.m
#implementation
#synthesize networkDelegate
-(void) initWithParams:(id) delegate
{
networkDelegate = delegate;
// Assign GET/POST vals, create request etc
[request startAsynchronous];
}
-(void) requestSucceded:(ASIHTTPRequest *) request
{
if([networkDelegate respondsToSelector:#selector(requestSucceded:)]) {
// Send the data to the controller object for it to use
...
}
}
-(void) requestFailed:(ASIHTTPRequest *) request
{
// Same as above. Send to request failed.
}
#end
And finally in my FirstViewController.h
#import "NetworkAccessClass.h"
#interface FirstViewController<NetworkAccessDelegate>
{
}
-(void) requestSucceded:(NSData *) data;
-(void) requestFailed:(int) responseCode;
#end
And the same in SecondViewController.h and so on.
Although this does decouple my Controllers from my Network class, I can't help feel it's wrong because the controllers in this case are acting as delegates or helper methods to the Network Class and not the other way round. Am I missing something basic? Or is this how it is?
Thanks,
Teja.
Delegates aren't "helper methods". Think of them as objects that get notified when something happens. (Although don't confuse them with "Notifications"--that's a different thing entirely.) In this case, your network class does it's stuff and then calls its delegate method on the View Controller that instantiated and fired, it to report the contents of that response to the view controller. The controller will then, presumably, update the view with the data that the network connector got. Classic delegate pattern, right there.
In order to better understand the startup, event queue, and methods within my application I'm trying to write a program that does two things: Play a beep at the startup and every time the user hits a button. So far it only plays when the user hits the button. I know there may be multiple ways to get the startup beep to play, but in order to work with initialization code I want to do it by calling my beep method from within the applicationDidFinishLaunching method of the AppDelegate.m file.
Here is my code:
Log.h
#import <Cocoa/Cocoa.h>
#interface Log : NSObject {
IBOutlet id button;
}
-(void)beepAndLog;
-(IBAction)buttonPressed:(id)sender;
#end
Log.m
#import "Log.h"
#implementation Log
-(void)beepAndLog {
NSLog(#"The Method Was Called!");
NSBeep();
}
-(IBAction)buttonPressed:(id)sender {
[self beepAndLog];
}
#end
And the applicationDidFinishLaunching method looks like this:
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
// Insert code here to initialize your application
[Log beepAndLog];
}
In the applicationDidFinishLaunching method, however, XCode warns me that
'Log' may not respond to '+beepAndLog'
and indeed, there is no beep and the log reads as follows:
MethodResponse[11401:a0f] +[Log
beepAndLog]: unrecognized selector
sent to class 0x100002100
("MethodResponse" is the name of my project, btw)
I'm unsure why Log wouldn't respond to beepAndLog, seeing as that's one of its methods. Am I calling it incorrectly? I have a feeling this will be painfully obvious to you more experienced people. I'm a newbie. Any help would be appreciated! Thanks!
There are two possibilities. Either you defined beepAndLog as an instance method, when you wanted a class method, or you want to call it on an instance when you called it on the class.
To change it to a class method, change the header to read:
+(void)beepAndLog;
and the implementation:
+(void)beepAndLog {
NSLog(#"The Method Was Called!");
NSBeep();
}
For the other solution, make sure you have an instance of class Log around (probably a singleton), and do something like:
[[Log logInstance] beepAndLog];
from your notification method. The Log class would need to look something like this:
Log.h:
#import <Cocoa/Cocoa.h>
#interface Log : NSObject {
IBOutlet id button;
}
+(Log *)logInstance;
-(void)beepAndLog;
-(IBAction)buttonPressed:(id)sender;
#end
Log.m:
#import "Log.h"
Log *theLog = nil;
#implementation Log
+(Log *)logInstance
{
if (!theLog) {
theLog = [[Log alloc] init];
// other setup (like hooking up that IBAction)
}
return theLog;
}
-(void)beepAndLog {
NSLog(#"The Method Was Called!");
NSBeep();
}
-(IBAction)buttonPressed:(id)sender {
[[Log logInstance] beepAndLog];
}